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| United States Patent |
5,756,636
|
|
Slack
, et al.
|
May 26, 1998
|
Isocyanate prepolymers produced from toluene diisocyanate residue
dissolved in toluene diisocyanate
Abstract
A substantially solid free isocyanate prepolymer is made by reacting an
isocyanate mixture which is made up of a toluene diisocyanate residue
containing monomeric toluene diisocyanate and optionally, additional
monomeric toluene diisocyanate in an amount such that the total NCO
content is at least 37% with a polyether polyol having an ethylene oxide
content of at least 30%. The polyether polyol has a molecular weight of
from about 200 to about 6,000 and a functionality of from 2 to 6. The
product prepolymers are particularly useful in the production of
polyurethanes.
| Inventors:
|
Slack; William E. (Moundsville, WV);
Pisipati; Jyothi S. (Wexford, PA)
|
| Assignee:
|
Bayer Corporation (Pittsburgh, PA)
|
| Appl. No.:
|
774278 |
| Filed:
|
December 27, 1996 |
| Current U.S. Class: |
528/59; 521/49.5; 525/452; 525/457; 525/458; 528/67; 528/76; 528/77; 560/25; 560/26; 560/336; 560/360 |
| Intern'l Class: |
C08G 018/10; C08G 018/76; C07C 269/02; C07C 271/26 |
| Field of Search: |
528/59,67,76,77
560/25,26,336,360
521/49.5
525/452,457,458
|
References Cited
U.S. Patent Documents
| 4143008 | Mar., 1979 | Zwolinski et al. | 528/67.
|
| 4251401 | Feb., 1981 | Reischl | 525/424.
|
| 4293456 | Oct., 1981 | Reischl | 524/589.
|
| 4297456 | Oct., 1981 | Reischl et al. | 525/452.
|
| 4311800 | Jan., 1982 | Reischl | 521/109.
|
| 4489177 | Dec., 1984 | O'Connor et al. | 528/67.
|
| 4507464 | Mar., 1985 | Rasshofer | 528/288.
|
| 4996242 | Feb., 1991 | Lin | 521/131.
|
| 5114986 | May., 1992 | Lin | 521/131.
|
| 5143945 | Sep., 1992 | Bodnar et al. | 521/130.
|
| 5216042 | Jun., 1993 | Daussin et al. | 521/160.
|
| 5290818 | Mar., 1994 | Nafziger et al. | 521/54.
|
| 5312888 | May., 1994 | Nafziger et al. | 528/67.
|
Primary Examiner: Sergent; Rabon
Attorney, Agent or Firm: Gil; Joseph C., Whalen; Lyndanne M.
Claims
What is claimed is:
1. A process for the production of a substantially solids free isocyanate
prepolymer having an isocyanate group content of from about 3 to about 40%
comprising reacting
a) an isocyanate mixture having a total isocyanate group content of at
least 37% which is composed of
1) a toluene diisocyanate residue containing at least 10% by weight
monomeric TDI obtained by phosgenation of toluene diamine having an
ortho-toluene diamine content of less than 0.5% and
2) monomeric toluene diisocyanate in an amount such that a total of from 60
to 99% by weight monomeric toluene diisocyanate is present in the
isocyanate mixture a), with
b) a polyether polyol having an ethylene oxide content of at least 30% by
weight, a molecular weight of from about 200 to about 6,000 and a
functionality of from about 2 to about 6 in amounts such that the total
NCO content of the prepolvmer reaction product is from about 3 to about
40%.
2. The process of claim 1 in which the polyether polyol has an ethylene
oxide content of at least 30% by weight and any additional alkylene oxide
groups are propylene oxide groups.
3. The process of claim 1 in which the polyether polyol has an ethylene
oxide content of at least 50% by weight.
4. The process of claim 1 in which the TDI residue 1) is present in the
isocyanate mixture a) in an amount of up to 35% by weight.
5. The process of claim 1 in which the isocyanate mixture a) has an
isocyanate group content of at least 39%.
6. The process of claim 1 in which the toluene diisocyanate residue is
produced by phosgenation of toluene diamine having an ortho-isomer content
of less than 0.1%.
7. The isocyanate prepolymer produced by the process of claim 1.
8. The isocyanate prepolymer of claim 7 having an NCO content of from about
3 to about 30%.
9. The isocyanate prepolymer produced by the process of claim 2.
10. A process for the production of a polyurethane comprising reacting the
isocyanate prepolymer of claim 7 with an isocyanate reactive compound.
Description
BACKGROUND OF THE INVENTION
The present invention relates to isocyanate prepolymers produced from
toluene diisocyanate ("TDI") residue dissolved in TDI, to a process for
the production of such prepolymers and to a process for the production of
polyurethanes from these prepolymers.
TDI is generally produced by phosgenating toluene diamine ("TDA"). In the
course of producing TDI by this process, a non-distillable by-product
which is commonly referred to as "TDI residue" or "TDI bottoms" is
generated. The amount of this by-product generated during phosgenation is
dependent upon the amount of ortho-toluene diamine ("o-TDA") present in
the amine starting material and the phosgenation conditions. Major
concerns in the production of TDI are, therefore, the amount of TDI
residue generated and whether such TDI residue is useful in other
applications.
The usefulness of a TDI residue is largely dependent upon the heat history
of that residue. That is, the longer the residue has been subjected to
high heat to remove monomeric TDI, the more difficult it becomes to work
with that by-product. It has generally been found that after the TDI
monomer content of the TDI residue has been reduced to a level below 10%,
the remaining residue is a solid at ambient temperature and is insoluble
in the commonly used solvents. Consequently, TDI residues containing less
than 10% monomeric TDI are not generally considered useful and are
disposed of by incineration.
The desirability of using the large quantities of TDI residue generated
during TDI production is evident from the prior art.
U.S. Pat. No. 4,293,456, for example, teaches that finely ground solid TDI
residue which is substantially free of monomeric TDI (i.e., generally
contains from 1 to 10% monomeric TDI) may be used as a reactive filler to
produce polyurethane plastics. It is therefore possible to recycle the
previously unusable TDI residue and to improve the mechanical properties
of plastics made with that finely ground residue. The TDI residue used in
this process may be water quenched and denatured or chemically modified by
reaction with carbonyl compounds, compounds reactive to isocyanate groups,
or carbodiimide groups. The TDI residue must, however, be size reduced to
less than 3 mm before it can be used.
U.S. Pat. No. 4,297,456 also teaches that TDI residue which is
substantially free of monomeric TDI (i.e., contains less than 7.5%
monomeric TDI) and insoluble in organic solvents may be used in the
production of molded articles and elastomers if that TDI residue is first
comminuted to a mean particle size of less than 800 m.mu.. This TDI
residue may be modified during or after grinding by reaction with water,
an amine, ammonia, a compound containing hydroxyl groups or a compound
containing carboxyl groups.
U.S. Pat. No. 4,507,464 teaches that a liquid isocyanate residue may be
obtained by phosgenating a primary polyamine such as TDA in the presence
of a compound selected from a specified group and having at least one
primary or secondary alcoholic hydroxyl group. The amine and
hydroxyl-group containing compound are used in quantities such that the
equivalent ratio of primary amino groups to hydroxyl groups is from
1:0.005 to 1:0.99 during the phosgenation. The residue remaining after the
desired isocyanate prepolymer has been removed is a liquid.
U.S. Pat. No. 5,290,818 discloses a process for producing rebond foam in
which the binder includes TDI distillation bottoms having a monomeric TDI
content of from 20 to 30%.
U.S. Pat. No. 5,312,888 also discloses a process for producing rebond foam
in which TDI residue is blended with methylene diphenyl diisocyanate or
polymethylene polyphenyl polyisocyanate and a hydroxyl compound to obtain
a binder which is then applied to shredded foam. Toluene diisocyanate may
optionally be included in the binder composition.
It would be advantageous to develop a method for using TDI distillation
residue to produce a urethane group-containing prepolymer that is
substantially free of solids.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a substantially solids
free isocyanate prepolymer produced from TDI residue.
It is also an object of the present invention to provide a process for
producing a substantially solids free isocyanate prepolymer from TDI
residue.
It is another object of the present invention to provide polyurethanes
which are produced from an isocyanate prepolymer formed from TDI residue.
It is a further object of the present invention to provide a process for
producing polyurethanes, particularly polyurethane foams, from isocyanate
prepolymers produced from TDI residue.
These and other objects which will be apparent to those skilled in the art
are accomplished by selecting a TDI residue generated by phosgenation of
TDA in which the o-TDA content was less than 0.5%. The TDI residue to be
used in the present invention has a total NCO content (i.e., the total NCO
content of monomeric TDI plus other isocyanate group containing materials)
of at least 37%. TDI residues containing at least 10% by weight monomeric
TDI and satisfying these criteria may be combined with additional toluene
diisocyanate in an amount such that at least 1% and up to 40% by weight of
the total amount of the isocyanate mixture is TDI residue and at least 60%
by weight of the mixture is monomeric TDI. The TDI residue or isocyanate
mixture containing TDI residue is reacted with a polyether polyol having
ethylene oxide present therein in an amount of at least 30% by weight to
form a urethane prepolymer having an isocyanate group content of from
about 3 to about 40%. Polyurethanes may be produced from these prepolymers
by reacting the prepolymer with an isocyanate-reactive compound in
accordance with known methods.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to isocyanate prepolymers produced from a TDI
residue or a mixture of TDI and TDI residue and reacted with a polyether
polyol having an ethylene oxide content of at least 30% and to the process
for producing such prepolymers.
The TDI residues useful in the practice of the present invention must
satisfy the following criteria: (1) the residue must have been generated
by the phosgenation of toluene diamine in which the o-TDA content was less
than 0.5%, preferably less than 0.1%, most preferably about 0; and (2) the
total isocyanate group content of monomeric TDI plus any other isocyanate
group containing material present must be at least 37%, preferably at
least 39%.
With respect to the first of these criteria, the o-TDA content of the
polyamine to be phosgenated may easily be determined by methods known to
those skilled in the art such as gas chromatography. If the o-TDA content
of the TDA is greater than 0.5%, the TDA may be treated (e.g., by
fractional distillation) to reduce the level of o-TDA to an acceptable
level. The phosgenation of TDA may be carried out by any of the methods
known to those skilled in the art. Upon completion of that phosgenation,
monomeric TDI is generally removed from the reaction mixture by
distillation. In accordance with the present invention, the reaction
mixture may be distilled until up to 90% of the monomeric TDI has been
recovered. If more than 60% by weight of the monomeric TDI has been
removed, TDI monomer is generally blended with the residue in an amount
sufficient to bring the total TDI monomer content of the residue to at
least 60% by weight. It is preferred, but not required, that any solvent
employed in the phosgenation process be removed prior to use of the TDI
residue in accordance with the present invention.
The TDI residue may be dissolved or otherwise combined with monomeric TDI
in an amount such that at least 1% and up to 40% by weight, preferably
from about 10 to about 38%, most preferably from about 30 to about 35% of
the total isocyanate mixture is TDI residue. The TDI residue plus TDI
must, however, be used in quantities such that at least 60%, preferably
from 60 to 99% by weight, of the total mixture or solution is monomeric
TDI.
It is, of course, possible to eliminate the need to dissolve TDI in a TDI
residue by using TDI which had not been recovered separately but which was
allowed to remain in the distillation vessel along with the TDI residue
(e.g., by discontinuing distillation of the phosgenation product mixture
prematurely).
The polyether polyol which is reacted with the TDI residue mixture or a TDI
residue containing mixture must have an ethylene oxide content of at least
30% by weight, preferably from about 30 to about 40% by weight, most
preferably from about 40 to about 60% by weight. Such polyether polyols
may be produced in accordance with any of the methods known to those
skilled in the art.
Polyether polyols useful in the practice of the present invention typically
have functionalities of from about 2 to about 6, preferably from about 2
to about 4, and molecular weights (number average determined by end group
analysis) of from about 200 to about 6,000, preferably from about 1,000 to
about 4,800. Examples of such polyether polyols include those obtained in
known manner by reacting one or more starting compounds which contain
reactive hydrogen atoms with alkylene oxides such as ethylene oxide,
propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran,
epichlorohydrin or mixtures of these alkylene oxides. Polyethers obtained
by addition of ethylene oxide alone or in combination with propylene oxide
are most preferred. Suitable starting compounds containing reactive
hydrogen atoms include polyhydric alcohols (described below as being
suitable for preparing polyester polyols); water; methanol; ethanol;
1,2,6-hexane triol; 1,2,4-butane triol; trimethylol ethane;
pentaerythritol; mannitol; sorbitol; methyl glycoside; sucrose; phenol;
isononyl phenol; resorcinol; hydroquinone; and 1,1,1- or
1,1,2-tris(hydroxyl phenyl )-ethane.
Other polyols, particularly those having a functionality of from 2 to 6 and
a molecular weight of from 200 to 6,000 (number average determined by end
group analysis) known to be useful in the production of polyurethanes
could also be included with the required polyether polyol. However, if
such other polyols are used, those polyols must be used in an amount such
that the ethylene oxide content of the total polyol mixture is at least
30%.
The TDI residue or TDI residue containing mixture is reacted with the
polyether polyol containing at least 30% by weight ethylene oxide in a
quantity such that the NCO content is from about 3 to about 40%,
preferably from about 3 to about 30%, most preferably from about 9 to
about 20%. This reaction may be carried out at temperatures of from about
20.degree. to about 120.degree. C., preferably from about 40.degree. to
about 90.degree. C., most preferably from about 50.degree. to about
70.degree. C. The prepolymer formed as a result of this reaction is clear
and substantially solids free (i.e., has a solids content of less than
0.5%).
The isocyanate prepolymers of the present invention may be used to produce
polyurethanes in accordance with any of the known methods by reacting them
with suitable isocyanate-reactive compounds, optionally in combination
with additives and processing aids such as catalysts, surfactants, blowing
agents, and crosslinking agents.
Suitable isocyanate-reactive compounds include polyether polyols, polyester
polyols, polyamines, aminopolyethers, water and any combination thereof.
The polyether polyols which may be reacted with the prepolymers of the
present invention include polyether polyols of the type used to produce
these prepolymers, polyether polyols in which less than 30% by weight is
ethylene oxide is present and polyether polyols in which no ethylene oxide
is present. Such polyether polyols may be produced in the same manner as
the polyether polyols used to produce the prepolymers of the present
invention with the exception that ethylene oxide need not be used in the
specified amounts and, in fact, need not be used at all.
Suitable polyether polyols will generally have a functionality of from
about 2 to about 6, preferably from about 2 to about 4, most preferably
from about 2 to about 3 and a molecular weight (number average determined
by end group analysis) of from about 200 to about 6,000, preferably from
about 1,000 to about 4,800, most preferably from about 2,000 to about
4,000.
Polyester polyols useful in the practice of the present invention typically
have functionalities of about 2 and molecular weights (number average
determined by end group analysis) of from about 400 to about 4,000,
preferably from about 600 to about 2,000. Examples of such polyester
polyols include the reaction products of polyhydric alcohols (preferably
dihydric alcohols to which trihydric alcohols may be added) and polybasic
(preferably dibasic) carboxylic acids. In addition to these polycarboxylic
acids, corresponding carboxylic acid anhydrides or polycarboxylic acid
esters of lower alcohols or mixtures thereof may also be used to prepare
the polyester polyols useful in the practice of the present invention. The
polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic and/or
heterocyclic and they may be substituted, e.g. by halogen atoms, and/or
unsaturated. Examples of suitable polycarboxylic acids include: succinic
acid; adipic acid; suberic acid; azelaic acid; sebacic acid; phthalic
acid; isophthalic acid; trimellitic acid; phthalic acid anhydride;
tetrahydrophthalic acid anhydride; hexahydrophthalic acid anhydride;
tetrachlorophthalic acid an hyd ride, endomethylene tetrahydrophthalic
acid anhydride; glutaric acid anhydride; maleic acid; maleic acid
anhydride; fumaric acid; dimeric and trimeric fatty acids such as oleic
acid, which may be mixed with monomeric fatty acids; dimethyl
terephthalates and bis-glycol terephthalate. Suitable polyhydric alcohols
include: ethylene glycol; 1,2- and 1,3-propylene glycol; 1,3- and
1,4-butylene glycol; 1,6-hexanediol; 1,8- octanediol; neopentyl glycol;
cyclohexanedimethanol; (1,4-bis(hydroxymethyl)cyclohexane);
2-methyl-1,3-propanediol; 2,2,4-trimethyl -1,3-pentanediol; triethylene
glycol; tetraethylene glycol; polyethylene glycol; dipropylene glycol;
polypropylene glycol; dibutylene glycol and polybutylene glycol, glycerine
and trimethylolpropane. The polyesters may also contain a portion of
carboxyl end groups. Polyesters of lactones, e.g. caprolactone or hydroxyl
carboxylic acids such as co-hydroxycaproic acid, may also be used.
Polyamines useful in the practice of the present invention will generally
have a functionality of from about 2 to about 4, most preferably from
about 2 to about 3 and a molecular weight (number average) of from about
400 to about 4,800, preferably from about 600 to about 4,000, most
preferably from about 800 to about 2,000. Such polyamines may be produced
by reductive amination of polyether polyols or by the cyanoethylation of
polyols followed by hydrogenation. Polyoxypropylene diamines, triamines
and mixtures thereof are preferred. Polymers containing both amino and
hydroxyl groups obtained by the partial amination of a polyol are also
useful in the practice of the present invention.
Aminopolyethers may also be used to produce urethanes from the prepolymers
of the present invention. Suitable aminopolyethers generally have a
functionality of from about 2 to about 4, preferably from about 2 to about
3 and a molecular weight (number average) of from about 400 to about
3,000, preferably from about 800 to about 2,000. Such aminopolyethers may
be produced by any of the known methods. Such methods are described in
greater detail in U.S. Pat. No. 5,510,535 which is incorporated herein by
reference. Examples of specific aminopolyethers which are particularly
useful in producing polyurethanes from the urethane prepolymers of the
present invention include Jeffamine J 2000 which is commercially available
from Texaco.
Short chain diols which may also be useful in the production of
polyurethanes from the prepolymers of the present invention typically have
molecular weights of from about 62 to about 400. Examples of suitable
diols include: 1,3-butanediol, 1,2-propylene glycol, and ethylene glycol.
Monofunctional and even small amounts of trifunctional and higher
functional compounds generally known in polyurethane chemistry may be used
to produce polyurethanes in accordance with the present invention. For
example, trimethylolpropane, glycerol and diethanol amine may be used
where slight branching is desired.
Catalysts, solvents, surfactants, blowing agents, and other additives known
to be useful in the production of polyurethanes may be used to aid the
polyurethane-forming reaction. Examples of catalysts useful for promoting
urethane reactions include di-n-butyl tin dichloride, di-n-butyl tin
diacetate, di-n-butyl tin dilaurate, triethylenediamine, bismuth nitrate,
N-methyl morpholine, diethyl ethanol amine, N,N-diethyl-3-diethylamino
propyl amine, dimethyl benzyl amine, any of the known tertiary amine
catalysts and organometallic catalysts.
Examples of useful additives include: colorants, cell openers, flame
retardants, antioxidants, and mold release agents.
Examples of suitable surfactants include: siloxane/poly(alkylene oxide)
copolymers such as those disclosed in U.S. Pat. Nos. 3,887,800 and
3,957,842 and any of the known fatty acid salts.
Examples of suitable blowing agents include: methylene chloride, acetone,
pentane, hexane, methyl formate and carbon dioxide.
Foams may be prepared in accordance with the present invention by mixing
the isocyanate prepolymer of the present invention with an isocyanate
reactive material and any of the additives typically used by those skilled
in the art and allowing the reaction to proceed to completion. Foams may
also be prepared by a two-step process in which the isocyanate prepolymer
of the present invention is first combined with an isocyanate-reactive
material and then, while the reaction of the prepolymer and
isocyanate-reactive material is proceeding, adding water, surfactant and
catalyst to form a "pour-in-place" foam.
Having thus described our invention, the following Examples are given as
being illustrative thereof. All parts and percentages given in these
Examples are parts by weight and percentages by weight, unless otherwise
indicated.
EXAMPLES
The materials used in the Examples which follow were:
Polyol A: a propylene glycol/propylene oxide/ethylene oxide adduct having
20% terminal ethylene oxide, a functionality of 2 and a molecular weight
of 4000.
Polyol B: a propylene glycol/propylene oxidelethylene oxide adduct having
30% terminal ethylene oxide, a functionality of 2 and a molecular weight
of 4000.
Polyol C: a propylene glycol/propylene oxide/ethylene oxide adduct having
50% terminal ethylene oxide, a functionality of 2 and a molecular weight
of 2000.
Isocyanate A: Toluene diisocyanate (80% 2,4-isomer and 20% 2,6-isomer)
containing 35% by weight TDI Residue (generated from TDA having an
ortho-isomer content of less than 0.5% by weight) and having a total NCO
content of 39.0%.
Isocyanate B: Toluene diisocyanate (80% 2,4-isomer and 20% 2,6-isomer)
containing 54% by weight TDI Residue (generated from TDA having an
ortho-isomer content of less than 0.5% by weight) and having a total NCO
content of 34.0%.
The procedure used in each of the Examples was as follows:
The indicated Isocyanate in the amount reported in the Table was heated to
60.degree. C. and the indicated Polyol was added in the amount reported in
the Table. The mixture was stirred at 60.degree. C. for 2 hours and then
cooled to 25.degree. C. The appearance, NCO content and viscosity of each
prepolymer is reported in the Table.
TABLE
______________________________________
Example 1 2 3* 4* 5*
______________________________________
Isocyanate
A A A B B
107.2 107.2 103.8 118.7 101.1
Polyol B C A A B
grams 257 219 248.8 235 200
Appearance
Clear Clear Turbid Turbid Turbid
with solids
with solids
with solids
settling out
settling out
settling out
NCO content
9.3% 9.9% 9.7% 9.7% 9.4%
Viscosity
4300 2704 -- -- --
mPa.s
(25.degree. C.)
______________________________________
*Comparative Example
Although the invention has been described in detail in the foregoing for
the purpose of illustration, it is to be understood that such detail is
solely for that purpose and that variations can be made therein by those
skilled in the art without departing from the spirit and scope of the
invention except as it may be limited by the claims.
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